The present invention is directed to a light waveguide having at least two coatings composed of plastic material, wherein the outer layer for forming a fixed or solid optical lead is applied directly on the inner layer lying therebelow and is constructed to be flame-retardant.
A flame-retardant light waveguide comprising an optical fiber having a primary coating covering the fiber and a secondary coating covering the primary fiber, which is flame-retardant, is disclosed in U.S. Pat. No. 5,204,928, whose disclosure is incorporated herein by reference thereto and which claims priority from the same Japanese Application as European 0 516 438. The outer layer is composed of a polyester elastomer to which ethylene bis-tetrabromophthalimide is added as a flame-retardant agent. Antimony trioxide can also be additionally employed as an auxiliary additive. The outer layer and the inner layer adhere firmly to one another so that the stripping of the outer layer, for example for splicing of a plug-type connection, is not possible or is only possible with great difficulty. Another difficulty is that, due to the employment of the bromine-containing flame-retardant agent, the outer layer is not halogen-free and can, therefore, not be considered as a flame-retardant, non-corrosive layer or an FRNC layer.
For better stripping of the outer protective layer, it is known to separate these from the solid, inner layer lying therebelow with a separate parting layer of, for example, a fluid or pasty material. The application of such an additional parting layer, however, requires an additional working step during the manufacturing process and is also accompanied by the difficulty that the materials employed for this separation layer are likewise not flame-retardant and/or form corrosive constituents when burned.